Magneto-optical properties of cobalt nanoparticles in porous silicon.

• Annealing exhaustively changes the shape of the cobalt nanoparticles. • Asymmetric hysteresis loop of the deposited cobalt is obtained. • Presence of quadratic magneto-optical Kerr effect (QMOKE) contribution in the response. • LMOKE and QMOKE contributions are provided by the hysteresis loop symmetrization and anti-symmetrization. We report on the magnetooptical response of cobalt nanoparticles deposited on porous silicon surface. The use of such unconventional surface leads to a random feature for crystal relaxation considerably different from those of the smoothed one. Interestingly, heat treatment of the silicon substrate shows a significant effect on the morphology of the cobalt nanoparticles. Annealing exhaustively changes the shape of the cobalt nanoparticles. The study of the magnetic properties of the elaborated samples shows a peculiar behavior. Noticeably, an asymmetric hysteresis loop of the deposited cobalt is obtained. This result is attributed to a quadratic magneto-optical Kerr effect (QMOKE) contribution which certainly finds its origins in the interaction between neighboring clusters. [ABSTRACT FROM AUTHOR]